Q.10 Describe the characteristic features, structure and function of the grassland ecosystem.
Ans. Grassland Ecosystem: -
This is a type of terrestrial ecosystem. Temperate grasslands occur in regions too dry for forests and too moist for deserts. The annual rainfall ranges between 25 to 75 cm and is usually seasonal; while, temperatures are moderate.
The highest abundance and the greatest diversity of large mammals are found in these ecosystems. The dominant animal species include wild horses, asses and antelope of Eurasia; herds of bison of Ameria; and the antelope and other large herbivores of Africa.
Structure and Function: -
The different components of grassland ecosystem, like others, are as follows:
Abiotic component: -
The abiotic components are the nutrients present in soil and the aerial environment. The essential elements like C, H, N, O, P, S etc., thus, are supplied by water, CO2, nitrogen, nitrates, sulphates, phosphates, etc. present in the soil of the area and in the atmosphere.
Biotic component: -
The biotic component of a grassland ecosystem has representatives from the three functional or metabolic groups which may be categorized as:
(i) Producer Organisms: -
In a grassland, the producers are mainly grasses; though, a few forbs and shrubs also contribute to primary production of biomass.
(ii) Consumer Oraganisms: -
In a grassland ecosystem, the consumers are mainly of three types - primary, secondary and tertiary consumers.
The primary consumers are herbivores feeding directly on grasses. These are grazing animals such as cows, buffaloes, sheep, goats, deer, rabbits, etc. Besides them, numerous species of insects, termites, etc. are also present.
The secondary consumers are the carnivores that feed on primary consumers (herbivores). These include animals like frogs, snakes, lizards, birds, foxes, jackals, etc.
The tertiary consumers include hawks, etc., which feed on secondary consumers.
(iii) Decomposers: -
The saprotropic organisms that are active in the decomposition of dead or decayed organic matter of different forms of higher life are many species of fungi, bacteria and actinomycetes.
Q.10. What is food chain? (AKTU. - 2012 - 13)
Ans. A food chain shows how each living thing gets its food. Some animals eat plants and some animals eat other animals. For example, a simple food chain links the trees & shrubs, the giraffes (that eat trees & shrubs), and the lions (that eat the giraffes). Each link in this chain is food for the next link. A food chain always starts with plant life and ends with an animal. Animals that eat only plants called herbivores. Animals that eat other animals are called carnivores.
In a food chain, energy is passed from one link to another. When a herbivore eats, only a fraction of the energy becomes new body mass the rest of the energy is lost as waste or used by the herbivores in movement. Likewise when a carnivore eats animal, only a portion of the energy from the animal food is stored in its tissues.
‘The further along the food chain you go, the less food (and hence energy) remains available.
Most food chains have no more than four or five links. There cannot be too many links in a single food chain because the animals at the end of the chain would not get enough food (and hence energy) to stay alive.
Most animals are part of more than one food chain and eat more than one kind of food in order to meet their food and energy requirements. These interconnected food chains form a food web.
A change in the size of one population in a food chain will affect other populations. This interdependence of the populations within a food chain helps to maintain the balance of plant and animal populations within a community.
Food chains follow a single path as animals eat each other. Example:grass (is eaten by a) grasshopper (which is eaten by a) frog (which is eaten by a) snake twhich is eaten by a) hawk
In nature ,there are two basic types of food chains, namely Grazing food chain and Detritus food chain.
Grazing Food Chain: -
These types of food chains originate from plants and go to grazing animals and then on to animal eaters. Some of the examples are:
Phytoplanktons—zooplanktons—fish, Grass—rabbit—fox—Lion
Detritus food Chains: -
These types of food chain goes from dead organic matter into micro organisms to organisms feeding on detrivores and their predators. This system is thus less dependent on solar energy.
The chain of energy transfring from one species to another can continues several more times, but it is eventually ends. It ends with the dead animals that are broken down and used as food or nutirtion by bacteria and fungi. As these organisms reffered to as decomposers, feed from dead animals, they break down the complex organic compounds into simple nutrients. The simple nutrients are returned to the soil and can be used again by the plants. The energy transformation chain starts all over again.
